High strength alloy steel for structural and pressure vessels



HIGH STRENGTH ALLOY STEEL FOR STRUC- TURAL AND PRESSURE v ssELs Joseph G. Althouse, Coatesville, Pa, assignor to Lukens Steel Company, Coatesville, Pa.,-acorpration of Pennsylvania No Drawingf Application May 23, 1 957v Serial No. 661,018

3 Claims. (Cl. 15- 124 1 This invention relates to alloy Steels and more particularly to low alloy, high strength" structural quality, .or flange and firebox quality steels. The overall production of the steels of this invention would be for the production of rolled plates, sheets, bars and rods. The invention further pertains to the production of forgings and structural shapes, in the heat treated condition, i. e., normalized, accelerated cool normalized, and stress relieved or tempered. i i r An object of the invention is the production of a molybdenum-nickel-vanadium-titanium steel which is in the low alloy-high strength category, andwhich can be developed for structural and pressure vessel uses of the type which require a high yield point combined with good ductility and weldability.

A further object of the invention is the production of such alloy steel wherein a specific combination of alloying elements can be varied within definite ranges to pro vide proper weldability and strength for varying thicknesses of plate. i g

j The foregoing objects are achieved in the present invention by the provision of a new and useful combination of alloying elements which together with iron are comaimed to produce an alloy steel having the desired tensile properties, toughness, ductility, high yield strengthwith good impact properties down to -40 F.

The molybdenum-nickel-vanadium-titaniurn steel of this invention can be produced by either the open hearth, or the electric furnace, using a fine grain practice, including making the proper addition of deoxidizer, such as aluminum, in order to obtain an inherent grain size of Me- Quaid-Ehn Number 5 or finer.

A steel made for overall purposes that is in accordance with the present invention will conform to the following chemical analysis range:

Percentage Carbon 0.08-0.30 Manganese 0.90-1.40 Phosphorous 0.040 maximum Sulphur 0.050 maximum Silicon 0.15-0.35 Nickel 1.25-1.75 Vanadium 0.05-0. 13 Molybdenum 0.10-0.30 Titanium 0.005-0.05 Copper 0.35 maximum Aluminum 0.03-0.10 Iron 1 Remainder 1 With the exception of incidental steel making elements.

lt has been found that alloy steels Within the foregoing ranges provide a high tensile steel with good impact properties down to -40 F. The yield strengths of these steels are equal to or superior to other high strength steels now being used in the industry.

An alloy material for the production of thin section sheet or plates, bars, rods or shapes under /2" maximum 2,853,379 Patented Sept. 23, 1958 thickness or cross-section would have chemicalanalysis and ranges of:

Percentage Carbon 0.80 -0.15 Manganese 0.90 -1.20 Silicon 0.15 -0.35 Nickel L25- -1.75 Vanadium 0.05 -0.10. Molybdenum 0.10 -0.20 Titanium 0.005-0.02 Aluminum 0.03 -0.10

Remainder iron containing incidental impurities. Material for the making of larger-cross sectionplates,

bars, rods or shapes would have chemical analysis ranges Percentage Carbon 0.18 -0.30 Manganese 1.20 -1.40 Silicon 0.20 -0.35 Nickel 1.50 -1.75 Vanadium 0.08 -0.13 Molybdenum 0.20 -0.30 Titanium i 0.005-0.05 Aluminum 0.04 -0 .10

Remainder iron containing incidental impurities.

Mechanical properties The mechanical properties of the alloys having the above noted ranges afternormalizing at 1650 F.-l725 F., and tempering or stress-relieving between 1100" and 1250 F. will be as follows:

Plates or Plates or v Plates or Sections Sections Sections 34 and over $4 to over 1% to Under 1n 1%, lncL, incL, in Thickness in thickness thickness Tensile Strength, p. s. i 100, 000- v1110;000- 3 100, 000- 125, 000 125,000 125, 000 Yield strength, min., p. s. i. at 0.2

percent nttset 80, 000 80, 000 75, 000 Elongation in 2", min. percent- 18.0 20. 0 20. 0 Reduction in area, min. percent-- 45. 0 55.0 55.0

The material after heat treatment will have impact properties, as tested by Charpy keyhole type test, of minimum 15 ft. lbs. at 40 F.

Cold bend tests will meet the requirements shown below when bent 180 degrees to an inside diameter which will have the following relation to the thickness of the specimen:

Ratio of pin Thickness diameter to thickness of specimen Up to 1%, incl 2 Over 1% to 3", incl 3 Plates or sections over 3" in thickness Tensile strength, p. s. i 100,000-125,000

Yield strength, min., p. s. i 80,000 Elongation in 2", min. percent 20.0 Reduction in area, min. percent 55.0

The material after this heat treatment will have impact properties, as tested by Charpy keyhole test, of minimum ft. lbs. at 40 F.

Cold bend test of reduced section, i. e., /z" square bars, shall bend 180 degrees to an inside diameter of once the thickness of the specimen.

The advantageous features of steel materials of this composition are:

(1) High yield strength and ultimate strength with good impact properties down to -40 F. These are obtained by use of air coolingfrom the normalizing temperature and stress relief rather than by aliquid quench and draw heat treatment.

(2) By use of an accelerated cooling in air blast, ater spray or water dip from1650 F. to below 1000 F.,

heavy gauge materialsor materials over 3" thick or in same cross-section-can be. produced having good low temperature impact properties.

(3) The properties of the material are obtained from azstt'ucture consisting of ferrite and finely dispersed pearlite, rather than one. resulting Irom tempered martensite, such as would he. ,obtainedon fully quenched and drawn material..

(4) The fabrication and welding. of this material are simplified with, the above structure.

Fabrication Plates 1" and under in thickness can be sheared to size. Plates over 1" will be gas cut to size. The gas cutting will be preceded by pre-heating the plate to 200 F. Forming of ,heads or bending of plates can be accomplished either cold or hot.

Welding characteristics are good if proper weld rod and good welding technique are applied.

The invention may be embodied in other specific forms without departing from the essential characteristics thereof. Hence, the present embodiments are therefore to be considered in all respects merely as being illustrative and not as being restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all modifications and variations as fall within the meaning and purview and range phur, 0.15-0.35 percent silicon, 1.25-1.75 percent nickel,v

0.05-0.13 percent vanadium, 0.10-030 percent molybdenum, 0.005-0.05 percent titanium, up to 0.35 percent maximum copper, 0.03-0.10 percent aluminum, and the remainder iron and incidental impurities.

2. A low alloy high structural strength steel suitable for thin section sheets, bars, rods or shapes having a maximum cross section of 3", said steel containing .08-0.l5 percent carbon, 0.90-1.20 percent manganese, 0.15-0.35 percent silicon, 1.25-1.75 percent nickel, 0.05-0.10 percent vanadium, 0.10-0.20 percent molybdenum, 0.005-

002 percent titanium, 0.03-0.10 percent aluminum, and

the remainder iron and incidental impurities.

3. A low'alloy high structural strength steel suitable for plates, forgings, shapes and bars of heavy cross section in excess of 3" thickness, said steel containing 0.18- 0.30 percent carbon, 1.20-1.40 percent manganese, 0.20- 0.35 percent silicon, 1.50-1.75 percent nickel, 0.08-0.13 percent vanadium, 0.20-0.30 percent molybdenum, 0.005- 0.05 percent titanium, 0.04-0.10 percent aluminum, and the remainder iron and incidental impurities.

References Cited in the file of this patent UNITED STATES PATENTS Leitner Dec. 13, 1938 OTHER REFERENCES Cone: Steel, vol. 95, No. 13, Sept. 24, 1934, page 44. Published by Penton Publishing Co., Cleveland, Ohio.

Epstein et al.: Metals Technology, vol. 3, No. 3, April 1936, page 14. Published by the American Institute of Mining and Metallurgical Engineers, Inc., New York, N. Y.

UNITED STATES PATENT OFFICE CERTIFICATE OF GEORRECTION Patent Noe 2,853,379 September 23, 1958 Joseph n Althouse It is herehfi certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 4, in the tabulation, under the heading "Percentage", first item, for "O.80=-O.,l5" reed 0O8=O,l5 column 4, line '7, for "O80=O30" read O,O8-=OOBO SEAL) 'ttest:

m; AXLINE ROBERT c. WATSON Attcsting' Oflicer Commissioner of Patents 

1. A LOW ALLOY HIGH STRUCTRAL STRENGTH STEEL SUITABLE FOR STRUCTURAL OR PRESSURE VESSEL USES AND HAVING IMPROVED WELDABILITY, SAID STEEL CONTAINING 0.80-0.30 PERCENT CARBON, 0.90-1.40 PERCENT MANGANESE, UP TO 0.040 MAXIMUM PERCENT PHOSPHOROUS, UP TO 0.050 PERCENT MAXIMUM SULPHUR, 0.15-0.35 PERCENT SILICON, 1.25-1.75 PERCENT NICKEL, 0.05-0.13 PERCENT VANADIUM, 0.10-0.30 PERCENT MOLYBNDENUM, 0.005-0.05 PERCENT TITANIUM, UP TO 0.35 PERCENT MAXIMUM COPPER, 0.03-0.10 PERCENT ALUMINUM, AND THE REMAINDER IRON AND INCIDENTAL IMPURITIES. 